As the voice coding technology matures (i.e., the ability to encode voice with a fewer number of bits), the ability for a wireless communication system to carry at least one additional voice path on a radio frequency (“RF”) communication path is desired. Due to the limited amount of RF spectrum available, there is an interest to take advantage of the improved voice coding technology in order to support the additional voice call(s) on the existing channel while still maintaining the existing RF modulation scheme, and the existing functionality of the system.
A disadvantage of supporting the additional voice call(s) on the existing channel is the reduction of the number of bits available for voice and signaling in each call. The reduction in the number of bits required to carry a voice session, however, does not wholly address the problem. Since voice communication paths also convey signaling and framing information, as the number of voice paths per RF channel increase, so does the need for additional signaling and framing information. Increasing the bit rate of the RF communication channel is not always possible as communication bandwidth or range will suffer.
FIG. 1 illustrates an existing communication protocol that supports a single voice path per channel; frequency division multiple access (“FDMA”) technology is a common solution to support a single voice path per channel. Systems utilizing this protocol have a sufficient number of bits available to dedicate fields for each type of signaling, such as synchronization signaling, link control signaling, and/or the like.
As illustrated in FIG. 2, the existing channel may be divided into two or more voice paths, each supporting an independent voice call; time division multiple access (“TDMA”) technology is an attractive solution to divide the existing channel into two or more voice paths. Although FIGS. 1 and 2 show a conversion from FDMA to TDMA, converting any access technology to another is applicable.
Thus, there exists a need for a method of selectively allocating a limited number of bits to support multiple signaling types on a low bit rate channel.